The long-term goal of the proposed research is to develop diagnostic tools for otitis media (OM) and other pneumococcal infections and research tools for studying pneumococcal pathogenesis. OM is a major public health problem in young children with an enormous economic burden in the US as well as in the world. S. pneumoniae not only is a major bacterial cause of OM but also causes additional life-threatening or invasive infections. Pneumococcal infection is one of the four killer infectious diseases and probably the world's single biggest killer of young children. Although S. pneumoniae is one of the most important human pathogens, the laboratory diagnosis of pneumococcal infections is still dependent on traditional microbiological methods and very few new methods are reliable enough for the laboratory diagnosis of pneumococcal infections. The traditional microbiological methods and tests not only are laborious but also have many limitations. There is an urgent need for new laboratory diagnostic tests for pneumococcal diseases, as the limitations of current diagnostic tests hinder the timely and accurate diagnosis of pneumococcal infections, which in turn negatively affects not only the treatment of the diseases but also the assessment of the effectiveness of control measures. Aptamers are small single-stranded nucleic acids that bind a molecular or cellular target with high affinity and their biochemical properties rival or are superior to those of antibodies in a variety of analytical, diagnostic, and potential therapeutic applications, particularly in ease of production, batch uniformity, shelf life, and cost. In this exploratory two-year grant application, we propose to develop aptamers against two major pneumococcal virulence factors, choline-binding protein A (CbpA, also known as PspC or SpsA) and pneumococcal surface protein A (PspA). Both virulence factors are multidomain multifunction proteins and play major roles in pneumococcal evasion of host immunity and pathogenesis. The molecular bases for their functions are the ability of CbpA to bind human complement factor H (FH) and the ectodomain of pIgR and the ability of PspA to bind apo- and holo-lactoferrin (LF) and to inhibit complement deposition. Specific Aim 1 is to develop aptamers against the virulence factors and Specific Aim 2 is to map where in the virulence factors the aptamers bind and develop aptamer beacons for the detection of the virulence factors. The proposed research will set up the stage for exploring the idea of using aptamers for the development of diagnostic tests for pneumococcal infections and provide research tools for visualizing pneumococcal pathogenesis. Based on the essential roles of pneumococcal virulence factors in pneumococcal pathogenesis and the ability of the developed aptamers to neutralize the two most important virulence factors, the proposed research will also set up the stage for testing the hypothesis of antivirulence strategy as a novel alternative/complementary strategy for combating pneumococcal resistance to classical antibiotics. PUBLIC HEALTH RELEVANCE:Otitis media, or middle ear infection, is a major public health problem in young children both in the US and in the world. Streptococcus pneumoniae not only is the major bacterial cause of otitis media but also causes additional life-threatening or invasive infections. The proposed research will set up the stage for exploring the idea of using aptamers for the development of diagnostic tests for pneumococcal infections and research tools for visualizing pneumococcal pathogenesis and for testing the hypothesis of antivirulence strategy as a novel potential strategy against otitis media and other pneumococcal infections.